Chemistry 20 – Unit 3B – Acids and Bases – FITB Notes
General Outcome:
I. I can _________________________________________________________________________
Topic A – Arrhenius Definition
Specific Outcomes:
I. I can _________________________________________________________________________
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II. I can _________________________________________________________________________
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III. I can _________________________________________________________________________
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Empirical properties are the ____________ properties of a substance
Acids, bases and neutral substances have ____________ that either:
1) distinguish them from each other, or
2) are the same for all
The following table outlines these empirical properties
Acidic Substances
Basic Substances
Neutral Substances
Svante Arrhenius first proposed theory on acids and bases
His theory was that some compounds form electrically ________ particles when in
solution
He almost failed his PhD thesis because __________ hadn’t yet been discovered!
Later, he won the Nobel Prize for this theory
His explanation of the properties of _____ and _____ is called the Arrhenius theory of
acids and bases
An Arrhenius acid is a ___________ substance that ionizes (because it is not ionic to
begin with!) to form hydrogen ions, _______, in water
An Arrhenius base is an _______ substance that dissociates to form hydroxide ions,
_______, in water
An acid will increase the [_______] (H+ molar concentration) in an aqueous solution
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A base will increase the [_______] (OH- molar concentration) in an aqueous solution
_______, a neutral substance, will increase the concentration of both ions (hence
“neutral”):
ex. phosphoric acid
ex. potassium hydroxide
Topic B – Modified Arrhenius Definition
Specific Outcomes:
I. I can _________________________________________________________________________
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II. I can _________________________________________________________________________
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Arrhenius definition of acids and bases is good for compounds that are already ______
or ______
It does not predict how acids and bases can form from “seemingly ________”
compounds
These compounds first need to _____ an acid or a base, then ___________ into H+ or
OH- (in ___ or more steps)
Use “modified” Arrhenius theory (“__________________” theory) for unusual
compounds
In modified Arrhenius theory:
1. The 1st step involves water reacting (___________) to form an acid or base
2. The 2nd step involves (___________) dissociating the acid or base into its ions
Steps to write a modified Arrhenius equation:
1. Write chemical formulas for the reactants (usually ignore group I, 2 and 7 ions) as:
2. If the solution formed (product) is:
acidic, write __________ ions, H3O+(aq), as the first product, or
basic, write __________ ions, OH-(aq), as the first product
3. Complete the 2nd product by determining the combination of _____ and _______
that balances the chemical equation
tip: it should be a recognizable ion, usually a common ___________ ion!
Substances that appear to be neutral may actually be ______ (ex. Na2CO3, NH3)
It has been found that not all bases contain the __________ ion as part of their
original chemical formula
A modified Arrhenius base is a substance that reacts with ______ to produce _______
ions in aqueous solution
ex.
Metallic oxides (Na2O, MgO, etc.) form bases in water (long way):
1)
2)
You may write it in a single step (short way):
You can write any modified Arrhenius base in a single step!
ex. sodium oxide (long way):
2
ex. sodium oxide (short way):
ex. ammonia (long way):
ex. ammonia (short way):
Some modified Arrhenius bases are actually just ___________ ions (ex. CO32-)
Normally, these polyatomic ions are balanced with a group I __________ ion that is
aqueous with the polyatomic ion (ex. Na+ in Na2CO3)
We ________ the spectator ion in our equation!
ex.
According to the original Arrhenius definition, when ______ ionize, they produce
H+(aq)
ex.
It has been found using analytical technology like X-ray crystallography that _______
ions do not exist in isolation in an aqueous solution
The hydrogen ion is extremely positive in charge and water molecules are very _____
It is highly unlikely that _________ ions would exist in water without being attracted
to the negative poles of other ______ molecules
This results in the formation of the hydronium ion:
A modified Arrhenius acid is a substance that chemically reacts with ______ to
produce _________ ions in aqueous solution
ex.
ex.
Non-metallic oxides (CO2, SO2 etc) form acids in water using 2 steps of chemical
reactions:
1)
2)
You may write it in a single step (short way):
You can write any modified Arrhenius acid in a single step!
ex. carbon dioxide (long way):
ex. carbon dioxide (short way):
Topic C – Strong and Weak Acids
Specific Outcomes:
I. I can _________________________________________________________________________
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The acidic and basic properties of a substance depend on two things:
1) The _____________ of the solution
2) The _________ of the acid or base
Not all acids and bases ____________ ionize (they don’t form all the ions they are
supposed to)!
This depends on the acid or base’s ________
An acid that ionizes almost _____ in water is called a strong acid (use a single arrow!)
ex.
100% of the HCl(aq) becomes _____ and Cl The concentration of the H3O+(aq) is the same as the concentration of the _____ it
came from
Strong acids compared with weak acids:
• Strong acids are __________ electrolytes
• Strong acids react at a _______ rate (a faster reaction) with metals
• Strong acids are fully ionized (more ions), so they have _______ electrical
conductivity
There are 6 strong acids:
• perchloric acid
HClO4(aq)
• hydrobromic acid
HBr(aq)
• hydroiodic acid
HI(aq)
• hydrochloric acid
HCl(aq)
• sulfuric acid
H2SO4(aq)
• nitric acid
HNO3(aq)
They are on the ______ of your periodic table!
A ______ acid does not ionize 100% and only a small percentage of the acid forms ions
in solution (not all ions get formed!)
ex.
We use the ____________ arrow for weak acids
Weak acids react much _____ vigorously with metals
This occurs because there are less _____ ions!
Topic D – Strong and Weak Bases
Specific Outcomes:
same as for Topic C
A base that dissociates _____ into ions in water is called a strong base
Soluble ionic hydroxides and metallic oxides are strong bases
ex.
ex.
Strong bases compared with weak bases:
• Strong bases are __________ electrolytes
• Strong bases react at a ________ rate (a faster reaction) with substances
• Strong bases are fully ionized (more ions), so they have _______ electrical
conductivity
A ______ base does not dissociate 100% and only a small percentage of the base forms
ions in solution
ex.
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We use the ____________ arrow for weak bases
Weak bases react at a lower rate because there are far less _____ ions
Topic E – Monoprotic and Polyprotic Acids
Specific Outcomes:
I. I can _________________________________________________________________________
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Acids that have only ____ removable hydrogen ion per molecule are called
monoprotic acids
ex.
Acids that contain ____ or more hydrogen ions that can ionize are called polyprotic
acids
Polyprotic acids are capable of giving away ________ hydrogen ions!
ex.
Acids with ____ hydrogens are diprotic; acids with _______ hydrogens are triprotic
When polyprotic acids ionize, only one hydrogen is ________ at a time, with each acid
formed becoming progressively ________
ex. sulphuric acid
Topic F – Monoprotic and Polyprotic Bases
Specific Outcomes:
same as for Topic E
Bases that react with water in only ____ _____ to form hydroxide ions are called
monoprotic bases
ex.
Bases that react with water in _____ or more steps are called polyprotic bases
ex.
As with polyprotic acids, only one _______ is formed at a time, and each new base
formed is ________ than the last
ex. carbonate ion
Topic G – Acid and Base Concentration
Specific Outcomes:
I. I can _________________________________________________________________________
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Arrhenius thought of water as a substance that ionizes:
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Odds of this self-ionization happening = _____ out of every 1,000,000,000 water
molecules
Overall:
The concentrations of hydronium ions [H3O+(aq)] and hydroxide ions [OH-(aq)] are
equal and constant in pure water:
By multiplying the two concentrations, we can get the Ion Product for Water
(constant, Kw), equal to __________________________:
We can use this information to perform calculations and decide whether a given
solution is acidic, basic or neutral:
a) If [H3O+(aq)] > [OH-(aq)]: _______
b) If [H3O+(aq)] < [OH-(aq)]: _______
c) If [H3O+(aq)] = [OH-(aq)]: _______
ex. If you have a solution where [H3O+(aq)] = 1.0 x 10-5 mol/L, what is [OH-(aq)]? Is the
solution acidic, basic or neutral?
Try these ones:
[H3O+(aq)] = 1.0 x 10-2 mol/L
[H3O+(aq)] = 1.0 x 10-7 mol/L
[OH-(aq)] = 1.0 x 10-1 mol/L
[OH-(aq)] = 1.0 x 10-13 mol/L
[H3O+(aq)] = 3.0 x 10-2 mol/L
[H3O+(aq)] = 6.2 x 10-6 mol/L
[OH-(aq)] = 9.1 x 10-5 mol/L
[OH-(aq)] = 6.0 x 10-9 mol/L
[OH-(aq)] = ?
[OH-(aq)] = ?
[H3O+(aq)] = ?
[H3O+(aq)] = ?
[OH-(aq)] = ?
[OH-(aq)] = ?
[H3O+(aq)] = ?
[H3O+(aq)] = ?
Topic H – pH
Specific Outcomes:
I. I can _________________________________________________________________________
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II. I can _________________________________________________________________________
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III. I can _________________________________________________________________________
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IV. I can _________________________________________________________________________
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V. I can _________________________________________________________________________
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______ Sorenson developed the pH scale
pH stands for “power of _________” (10x)
It is used because it takes too long to write out very small ______ concentrations!
At 25°C (standard conditions), _____ solutions have a pH that falls between 0.0 and
14.0
It is possible to have a __________ pH and a pH ______ 14
The pH scale is ____________ (10x)
If pH goes down by 1, [H3O+(aq)] concentration goes up ___ times
If pH goes up by 1, [H3O+(aq)] concentration goes down ___ times
ex. A solution with pH of 8.0 is ____ times _____ acidic than a solution of pH 10
ex. A solution with pH of 5.0 is ____ times _____ acidic than a solution of pH 2.0
Sorensen’s pH scale:
We can calculate [H3O+(aq)] from the pH:
New sig fig rule: when reporting pH or pOH values, only the numbers to the _____ of
the decimal place count as significant (ex. use the addition-subtraction rule for this!!)
________ places of pH correspond to the sig-figs of the H3O+ molar concentration!
Try these:
pH = ?
[H3O+(aq)] = 1.0 x 10-10 mol/L
+
-2
[H3O (aq)] = 1.0 x 10 mol/L
pH = ?
[H3O+(aq)] = 6.8 x 10-3 mol/L
pH = ?
+
-6
[H3O (aq)] = 9.6 x 10 mol/L
pH = ?
You could be given information about an acid (ex. H3PO4) and may have to:
a) Write the complete _____________ equation
b) Calculate the original _____ concentration
c) Calculate [H3O+(aq)] using ion concentration and the ____ _____
d) Calculate [OH-(aq)] using ___ and [H3O+(aq)]
e) Calculate ____ from [H3O+(aq)]
ex. A chemist dissolves 6.30 g of H2SO4(aq) in 750 mL of water. What is [H3O+(aq)],
[OH-(aq)] and pH?
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You could also be given the pH and asked to calculate [H3O+(aq)], the reverse log:
Calculate [H3O+(aq)] for a pH of 4.0
Try these: pH = 6.2, 13.4, 7.0, -0.23, 15.70
Topic I – pOH
Specific Outcomes:
same as outcomes ii, iii and iv for Topic H
Just as pH is based on [H3O+(aq)], pOH is based on __________
“p” just means “_____” (remember “power of”)
At SATP conditions, pH + pOH = ___
You can calculate pH from pOH and vice versa:
pH compared with pOH on a scale:
To calculate the pOH or the [OH-(aq)], use the same formulas as pH but substitute the
[OH-(aq)] values:
Try these:
[OH-(aq)] = 1.0 x 10-11 mol/L
[OH-(aq)] = 6.22 x 10-2 mol/L
[OH-(aq)] = 9.411 x 10-6 mol/L
[OH-(aq)] = 2 x 10-6 mol/L
[OH-(aq)] = 11 mol/L
pOH = 1.0
pOH = 13.2
pOH = 6.9
pOH = 0.786
pOH = 15.2
pOH = ?
pOH = ?
pOH = ?
pOH = ?
pOH = ?
[OH-(aq)]
[OH-(aq)]
[OH-(aq)]
[OH-(aq)]
[OH-(aq)]
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=?
=?
=?
=?
=?
You could be given information about a base (ex. NaOH) and may have to:
a) Write a complete ____________ equation
b) Calculate the original _____’s concentration
c) Calculate [OH-(aq)] using ____ concentration and the mole ratio
d) Calculate _____ from [OH-(aq)]
e) Calculate __________ from [OH-(aq)]
f) Calculate pH from [H3O+(aq)] or _____
Topic J – Measurement of pH
Specific Outcomes:
I. I can _________________________________________________________________________
_____________________________________________________________________________
II. I can _________________________________________________________________________
pH can be measured using :
a) acid-base indicators, to the nearest _______ number
b) a pH meter, to ___ decimal places
An acid-base indicator is any chemical that changes _______ in an acidic or basic
solution
Indicators can be:
a) dried onto strips of ______ (ex. litmus paper, pH paper)
b) _________ (ex. bromothymol blue, universal indicator, indigo carmine, etc)
c) made from _________ substances (ex. tea, red cabbage juice, grape juice)
Each indicator has a specific pH ______ where it will change colour
You can use a combination of ___________ to determine the approximate pH of a
solution
Using a pH meter is the most ________ method
A pH meter has an ___________ that compares the [H3O+(aq)] in the solution to a
known standard, giving a digital readout of the pH
Common indicators, pH and colour changes:
• bromocresol green – ___ (yellow) to ___ (blue)
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• methyl red – ___ (red) to ___ (yellow)
• chlorophenol red – ___ (yellow) to ___ (red)
• bromothymol blue – ___ (yellow) to ___ (blue)
• phenol red – ___ (yellow) to ___ (red)
• phenolphthalein – ___ (colourless) to ___ (pink)
• methyl violet – ___ (yellow) to ___ (blue)
• orange IV – ___ (red) to ___ (yellow)
• methyl orange – ___ (red) to ___ (yellow)
• indigo carmine – ___ (blue) to ___ (yellow)
ex. Determine the approximate pH of a solution with the following indicator colours:
blue in bromocresol green, yellow in bromothymol blue.
ex. For a solution of pH of 5.0, suggest what the indicator colours are when methyl
red and chlorophenol red are used.
Topic K – Neutralization of Acids and Bases
Specific Outcomes:
I. I can _________________________________________________________________________
The reaction between an acid and a base is a reaction between ___________ and
____________!
The products of neutralization (an ionic compound and water) are both ________
In an acid-base reaction between a strong acid (______) and a strong base (_____),
the most important product is always water:
Two ways to deal with acid or base spills are:
1) _____________: always use a weak acid or base, so you aren’t left a new spill
involving a strong acid or strong base!
• neutralize a strong acid with solid sodium bicarbonate (________)
• neutralize a strong base with an acetic acid solution (_________)
2) _________: reduce the concentration of an acid or base by adding more water
• diluting an acid will decrease the [________] until a pH of ___ is reached
• diluting a base will decrease the [________] until a pH of ___ is
reached
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